

in V' :!('!!'- v -; . f *unT .^ '. 



PLATE LIV. 



PAGE. 



Fig. 1. PHYLLOPOKINA DA~VSONI Ulr 331 



1, 1 a, 1 b. Sections passing through the branohe . near the middle of their 



thickness, x!8. 

 1 p. A slightly oblique seotion. showing mature form of zooscial apertures, 



and accessory pores, x!8. 

 1 d. A vertical seotion. 

 1 e. If, 1 g. 1 h, 1 i. Five transverse sections showing the moderate keel. 



The zooecia appear different in each because each section I'euts them 



at a different point in their length, x!8. 



Fig. 2. FENESTELLA BELLISTRIATA ? Hall 331 



Section showing straight mesial line, and oblique walls, between the 

 ends ol the zooecia, x!8. Compare with flgs. 1 b and 4. 

 Niagara group, Waldron, Ind. 



Fig. 3. FENESTELLA VEBA Ulrich. (See also PI. XLIV) 535 



Section, xlS, showing structure at different levels. 

 Hamilton group, Buffalo, Iowa. 



Fig. 4. FENESTELLA INJBQUALIS Ulr. (See also pi. LID 554 



4. Deep section, x!8, showing primitive portion of zomaia with the inferior 



hemiseptum in those of the right branch, and the inflections produced 



by the superior one in those of the left branch. 

 4 a. Portion of section nearer the level of the cell apertures, x!8. The depths 



at which the section passes through the branch increases gradually 



from below upwards. 



Upper Coal Measures, Sangamon Co., 111. 



Fit,'. .'.. FENESTELLA EEOALIS Ulrich. (See also pi. L) 638 



Section, x!8, showing the large zooecia and the minute tubuli which 



pierce the outer crust. 



Keokuk group, Kings Mountain, Ky. 



Fig. (). ISOTBYPA QOXHLANDIOA Ulr 678 



(i. Horizontal section, x!8. showing form and arrangement of cells and, on 

 the left side, the lower portion of the keel. 



C a, ti 6, 6 c. Represent three transverse sections; a. a branch with dissepi- 

 ments and keel; b, two branches with the keel united; and c, a branch 

 just about to bifurcate, with two keete. 

 Upper Silurian, Gotland. 



